1. Field
The present invention relates to allowing computational efficiency of the basic transform domain approach to be achieved by first artificially extending the pilot support to move the effective edges of the pilot data further from the channel span of interest in broadband channel interpolation.
2. Background
Modern air-interface standards employ transit waveforms where known “pilot” tones are placed at regular location in the time frequency grid, wherein these pilots allow the channel to be estimated at the receiver at these locations, since the channel input is perfectly known. That is, by collecting the received signal at set pilot locations which occur at the same time but at different frequency locations, a receiver can interpolate the entire broadband frequency response for this time location.
Similarly, the entire time response for a given frequency location can be interpolated, so that, in this way, the computationally intensive two-dimensional time frequency channel interpolation is decomposed into two independent one dimensional interpolation problems (i.e. first in frequency and then in time).
However, to achieve the frequency domain interpolation with reasonable complexity, it is common to employ standard convolutional approaches, such as zero insertion between pilots followed by linear filtering. To minimize complexity this upsampling is implemented by employing a transform domain interpolation, i.e. a discrete inverse Fourier transform (IDFT, implemented through a butterfly decomposition as an IFFT with some mix of prime radixes) of the signal samples at the regularly spaced pilot locations followed by a zero padding operation in the complimentary transform domain together with any transform domain averaging and/or denoising), and a larger size forward FFT is employed to obtain uniformly interpolated samples in the original domain.
However, these methods suffer from distortion at the edges of the sample support due to the failure of a convolutional interpolator at the edges of the pilot data support (i.e. Gibb's phenomenon). This results in decreased channel quality at the edge tones, and ultimately in a loss of information throughput, thereby limiting the rate and quality of the overall communication link.
There is a need to provide a method of channel estimation at the receiver in a wireless communication system that provides computational efficiency of the basic transform domain approach to be accomplished by first extending the pilot support to move the effective edges of the pilot data further from the channel span of interest.